The Twenty-07 Study was set up in 1986 in order to investigate the reasons for differences in health by socio-economic circumstances, gender, area of residence, age, ethnic group, and family type.
4510 people are being followed for 20 years. The initial wave of data collection took place in 1987/8, when respondents were aged 15, 35 and 55. The final wave of data collection took place in 2007/08 when respondents were aged 35, 55 and 75.
In this way the Twenty-07 Study provides us with unique opportunities to investigate both the changes in people's lives over 20 years and how they affect their health, and the differences in people's experiences at the same ages 20 years apart, and how these have different effects on their health.

The Mexican Health and Aging Study (MHAS) started as a prospective panel study of health and aging in Mexico.
MHAS is nationally representative of the 13 million Mexicans born prior to 1951. The survey has national and urban/rural representation. The baseline survey, in 2001, included a nationally representative sample of Mexicans aged 50 and over and their spouse/partners regardless of their age. A direct interview was sought with each individual and proxy interviews were obtained when poor health or temporary absence precluded a direct interview.
The sample was distributed in all 32 states of the country in urban and rural areas. Households in the six states which account for 40% of all migrants to the U.S. were over-sampled. A sub-sample was selected to obtain anthropometric measures.

The Osteoarthritis Initiative (OAI) is a multi-center, longitudinal, prospective observational study of knee osteoarthritis (OA). The overall aim of the OAI is to develop a public domain research resource to facilitate the scientific evaluation of biomarkers for osteoarthritis as potential surrogate endpoints for disease onset and progression.